A Palestinian man who allegedly dumped handfuls of yellow powder in a Brooklyn mailbox will remain in custody pending test results on the substance from the city’s Department of Health.

Federal prosecutors yesterday charged Kamal Dawood, 51, with “maliciously injuring” a mailbox, a charge with a possible sentence of up to three years.

A mail carrier discovered the powder in the mailbox, near the intersection of Marcus Garvey Boulevard and Lafayette Avenue, after two witnesses reported seeing Dawood tampering with it. Dawood claims he never opened the mailbox, but merely set a cup of coffee on it while he smoked a cigarette.

He also faces state charges of reckless endangerment and obstructing governmental administration, both misdemeanors.